How to Configure Docker Private Registry in Rocky Linux 8

In this article, you will learn how to configure Docker Private Registry in Rocky Linux 8.

 

Table of Contents:

• What is Docker Private Registry?
• Environment Specification
• Updating Linux Software Packages
• Configure Docker Private Registry
• Conclusion

 

What is Docker Private Registry? :

Docker creates containers from Docker images. These images are provided by Docker Hub, a centralized public registry that contains various official and unofficial images of almost every software in the world. However, there are situations, when you require an on-premises Docker Private Registry to create and share custom docker images amongst your organizational units.

Docker Private Registry has a few advantages over Docker Hub, some of them are:

• Since, the Docker Registry is located on premises, therefore it increases availability and speed.
• Organization’s private images are kept within the Organization.
• Provides user authentication to restrict unauthorized access.
• Provides SSL based encryption for better security.

Here, we are using the Docker Engine CE to configure a Private Docker Registry. Therefore, it is advised that you should read Docker Deep Dive for some basic level understanding of Docker technology.

Recommended Online Training:Hands on With Docker & Docker Compose From a Docker Captain

 

Environment Specification:

We are using a minimal Rocky Linux 8 virtual machine with following specifications.

• CPU - 3.4 Ghz (2 cores)
• Memory - 2 GB
• Storage - 20 GB
• Operating System - Rocky Linux 8.6 (Green Obsidian)
• Hostname – docker-01.centlinux.com
• IP Address - 192.168.116.128 /24

 

Updating Linux Software Packages:

We are using the same Linux based Docker Server that we have configured in our previous installation guide.

By using a ssh client, connect with docker-01.centlinux.com as root user.

Refresh yum cache of your Linux server.

# dnf makecache
Rocky Linux 8 - AppStream                       1.9 kB/s | 4.8 kB     00:02
Rocky Linux 8 - BaseOS                          1.0 kB/s | 4.3 kB     00:04
Rocky Linux 8 - Extras                          974  B/s | 3.5 kB     00:03
Rocky Linux 8 - Extras                          2.7 kB/s |  11 kB     00:03
Docker CE Stable - x86_64                       5.0 kB/s | 3.5 kB     00:00
Metadata cache created.

Execute following command to update Linux software packages.

# dnf update -y

Check the Linux Kernel and Operating System versions.

# uname -r
4.18.0-372.13.1.el8_6.x86_64

# cat /etc/system-release
Rocky Linux release 8.6 (Green Obsidian)

Check the version of Docker that is being used in this article.

# docker version
Client: Docker Engine - Community
 Version:           20.10.17
 API version:       1.41
 Go version:        go1.17.11
 Git commit:        100c701
 Built:             Mon Jun  6 23:03:11 2022
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.17
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.17.11
  Git commit:       a89b842
  Built:            Mon Jun  6 23:01:29 2022
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.6.6
  GitCommit:        10c12954828e7c7c9b6e0ea9b0c02b01407d3ae1
 runc:
  Version:          1.1.2
  GitCommit:        v1.1.2-0-ga916309
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

 

Configure Docker Private Registry:

List the locally available Docker images in your server.

# docker images
REPOSITORY   TAG       IMAGE ID   CREATED   SIZE

Docker Hub provides an image for Docker Registry.

You can download it and use to create your on-premises Docker Private Registry.

Pull the registry image from Docker Hub.

# docker pull registry
Using default tag: latest
latest: Pulling from library/registry
2408cc74d12b: Pull complete
ea60b727a1ce: Pull complete
c87369050336: Pull complete
e69d20d3dd20: Pull complete
fc30d7061437: Pull complete
Digest: sha256:bedef0f1d248508fe0a16d2cacea1d2e68e899b2220e2258f1b604e1f327d475
Status: Downloaded newer image for registry:latest
docker.io/library/registry:latest

Create a directory to use as a consistent storage for Docker Containers.

# mkdir -p /opt/docker/containers/docker-registry/registry

Start the Docker Container with following command.

# docker run -d \
> --name docker-registry \
> --restart=always \
> -p 5000:5000 \
> -v /opt/docker/containers/docker-registry/registry:/var/lib/registry \
> registry
826777fa276a49f117e0b6300b036bc3f84ae5aa0a27e124a5a4a20c0c13b3e0

The service port 5000/tcp of Registry container is mapped with 5000/tcp of Docker host.

Therefore, you have to allow this service port in Linux firewall, so the network machines can access it.

# firewall-cmd --permanent --add-port=5000/tcp
success
# firewall-cmd --reload
success

Now, pull an image from Docker Hub. 

We prefer to pull Alpine Linux image, because it is smaller in size.

# docker pull alpine
Using default tag: latest
latest: Pulling from library/alpine
2408cc74d12b: Already exists
Digest: sha256:686d8c9dfa6f3ccfc8230bc3178d23f84eeaf7e457f36f271ab1acc53015037c
Status: Downloaded newer image for alpine:latest
docker.io/library/alpine:latest

Now, tag the alpine image as follows, and make it ready to add into your Docker Private Registry.

# docker tag alpine:latest localhost:5000/alpine

Push the Alpine image into Local Docker Registry.

# docker push localhost:5000/alpine
The push refers to repository [localhost:5000/alpine]
2408cc74d12b: Pushed
latest: digest: sha256:686d8c9dfa6f3ccfc8230bc3178d23f84eeaf7e457f36f271ab1acc53015037c size: 527

Get the list the locally available images of Alpine Linux.

# docker images | grep alpine
alpine                  latest    e66264b98777   5 weeks ago   5.53MB
localhost:5000/alpine   latest    e66264b98777   5 weeks ago   5.53MB

You can see that, one image is available from Docker Hub while the other is available via your Docker Private Registry.

 

Conclusion:

In this article, you have learned how to configure Docker Private Registry in Rocky Linux 8.